Fancy importing a subset of some product attributes on a per-store basis, whilst keeping the attributes that weren't imported using the defaults?
Tough, you can't!
Well, not with dataflow anyway. This card covers how Magento handles product saves, and the dataflow product adapter 'suffers' from this issue (by the way, the adapter class is Mage_Catalog_Model_Convert_Adapter_Product in case you fancy taking a look, the parse() method is where the magic happens).
The way I got around this was to create an adapter class. I subclassed Mage_Dataflow_Model_Convert_Adapter_Abstract and implemented a saveRow() method (the default adapter method) which used the logic in the Makandra card mentioned previously. I didn't subclass Mage_Catalog_Model_Convert_Adapter_Product, because it seemed to have a lot of unused stuff in it, which I didn't want or need.
I'm not sure how the ImportExport module works in this regard.
